We just started spelling this year (third grade). DH and I are REALLY good spellers, but I learned when I taught school that some people just have this ability and some do not. DS seems to be in the not camp; for the life of him, he cannot figure out what vowel goes in a word. Last year, he got panicky anytime I suggested he just guess how to spell a word; he likes to do things right. So, we have spent a whole semester on the vowels in very short, very familiar words. We made the lists from what he's reading; he's an avid reader, and I can see big improvement that seems related to the reading, like spelling words much more difficult than the his list that he struggles with. He's beginning to believe he CAN spell, but I'm not sure why he ever thought he couldn't.
Very long way of saying- we started in the third grade. First grade dd is teaching herself how to spell since I just WON't teach her to read (not true).